Currently there is great interest in the effects in early adulthood of asthma, increased bronchial responsiveness, markers of allergy and smoking on pulmonary function level and in the effects of these same risk factors on subsequent decline in pulmonary function, because these early adult factors presumably profoundly influence the risk for COPD. Extensive community-based data on the above named risk factors and adequate follow-up data on pulmonary function in an original sample of over 2000 subjects aged 18-35 years, followed a maximum of 21 years, offer the unique opportunity to study the prognostic significance of the above named risk factors for COPD. Specifically, the questions to be studied include whether the above named risk factors reduce the maximally attained level of pulmonary function n early adulthood, foreshorten the postulated stability of level of pulmonary function between age 18 and 35 and/or unfavorably affect subsequent decline in level of pulmonary function. To do this, FEV1/h2, VC/h2 and FEV1/IVC will be studied, using graphic smooth techniques and regression analyses techniques on both cross-sectional and longitudinal datasets. In addition, the investigators will test the hypothesis stating that early adult symptoms of asthma, increased bronchial responsiveness, markers of allergy influence who becomes a smoker, influence the amount smoked and/or influence who stops smoking relatively early in adult life, using logistic regression analyses and survival analyses.